Most spinnerbaits are about the same size. Skirt sizes are pretty much standard. Yes arm lenth can vary.
The weight of the head and size/style of blade, trailer if used determine the fall rate.
So by saying 3/4 oz, what do you want it to do? What depth and what speed retrieve? Do you need vibration or more flash?
Here ya go.
http://www.siebertoutdoors.com/Compact-Spinnerbait-009.htm